This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application entitled CARRIAGE ASSEMBLY OF RECIPROCATING PRINTER HEAD filed with the Korean Industrial Property Office on Feb. 13, 2001 and there duly assigned Ser. No. 2001/6980.
1. Field of the Invention
The present invention relates to a printer employing a movable print head, and more particularly, to a carriage assembly of a printer employing a movable print head, which has an improved structure capable of minimizing unstable movement of the carriage, and error in the concentricity of contacting portions of the carriage and a guiding rod.
2. Description of the Related Art
A carriage for a carriage assembly has to move along a guiding rod to print the full width on a sheet of recording medium. Carriages can be made of metallic material but this provides a heavy load to the guiding rod. Therefore carriages are generally made out of synthetic resin made by injection molding or machining. In addition, the resin contains an expensive fluoride additive to the resin to provide high lubricity between the carriage and the guiding rod. Unfortunately, this fluoride additive is used to produce the entire carriage instead of just the portions of the carriage that are in contact with the guiding rod resulting in expensive manufacturing costs to make a carriage.
Occasionally, two bosses, each being perforated by a hole, are needed in the design of the carriage. Often, the two bosses, and thus the two holes, are spaced apart by a distance. As is often the case, these two holes are not perfectly aligned to allow a straight guiding rod to easily and smoothly pass through. What is needed is a mechanism that is easy and inexpensive to manufacture, and that can allow a guiding rod to smoothly and frictionlessly pass through both holes of a carriage of a print head, even when the two holes are not aligned perfectly.
It is therefore an object of the present invention to provide a carriage assembly of a printer employing a movable print head, which has an improved structure capable of reducing friction between a carriage and a guiding rod.
It is also an object of the present invention to provide a structure for a carriage assembly that aligns the axes of the carriage and the guiding rod with each other.
It is yet another object of the present invention to provide bushings that attach to a carriage rod, the bushings being coextensive with the width of the bosses of the carriage.
It is still another object of the present invention to provide a carriage assembly that is not spring loaded by a coil spring between the bosses and around the guiding rod.
It is a further object of the present invention to provide spring type supporting plates that attach to the bosses and bushings to force the bushings to remain in sockets in the bosses.
It is yet another object of the present invention to provide a carriage having bosses which are perforated by a hole, the side walls of the hole tracing out a portion of a sphere, the outer surface of the bushings that fit within the hole in the bosses tracing out a surface of a sphere that is concentric to the sphere of the sidewalls of the hole in the bosses such that the radiuses of the two spheres differ substantially so as to allow the guiding rod to rotate in various directions when fitted into one hole in a boss.
It is also an object of the present invention to provide a carriage for a carriage assembly having a print head, the carriage being light weight, inexpensive to manufacture and essentially frictionless where the carriage meets the guiding rod.
Accordingly, to achieve the above objects, there is provided a carriage assembly of a printer employing a cartridge with a movable print head, and which is supported by a guiding rod. A carriage is installed to be movable within a predetermined distance along the guiding rod, the carriage assembly including a pair of bosses provided at each side of the carriage so as to be spaced a predetermined distance from each other, the bosses being perforated by bearing supporting holes, each inner circumferential surface of which is formed to have a predetermined radius of curvature, and a plurality of bearing bushings installed in the respective bearing supporting holes of the bosses, each outer circumferential surface of which has a different predetermined radius of curvature corresponding to that of the boss hole so as to make a spherical pair with the corresponding boss hole, each bearing bushing being provided with a shaft through-hole through which the guiding rod can pass slidably.